Antitumor Activity of a Polychlorinated Biphenyl Mixture, Aroclor 1254, in Rats In-oculated With Walker 256 Carcinosarcoma Cells2

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Abstract
The effects of a polychlorinated biphenyl (PCB) mixture, Aroclor 1254, on the transplantability and growth of the Walker 256 carcinosarcoma in male Sprague-Dawley rats were investigated. Repeated ip injection (100–200 mg PCB/kg) during tumor development resulted in a dose-dependent inhibition of tumor growth. When small numbers of tumor cells (103) were in-oculated, the number of tumor takes in PCB-treated animals was reduced and the latent period for the tumors that did develop was increased. When large numbers of tumor cells (107) were in-oculated, host survival time significantly increased in PCB-treated rats. Furthermore, whereas all controls exhibited progressive tumor growth after the inoculation of 107 tumor cells, complete tumor regression occurred in 25% of the animals treated with 200 mg PCB/kg. Preconditioning of the host with PCB for 5 days before tumor cell inoculation was equally effective in inhibiting primary tumor growth as was treatment with PCB during the first 5 days after tumor cell injection. If PCB exposure was delayed until after the tumor was established, the growth of the primary tumor was less effectively inhibited. Delayed PCB treatment, however, was more effective in prolonging host survival and decreasing metastases than was pretreatment or early treatment with PCB. The effect of PCB on survival time of animals bearing the ascites form of the Walker tumor was also assessed.

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